1. Field of the Invention
The present invention relates to a root canal filling material that is used for dental remedies and to a method for filling a root canal upon heat softening during the root canal treatment. In particular, the invention relates to a root canal filling material with improved filling operability and adhesion to root canal walls.
2. Description of the Background
As to the matter of remedies for dental pulp disease and apical periodontitis, normally in root canal treatment, a root canal filling material is employed which is a substance which is not only materially safe, but which is also safe to living bodies upon filling a root canal after extirpation of the dental pulp, thereby keeping a tooth root harmless against periodontal tissue. There are many variations of root canal filling material. Of these, most frequently used is a thin needle-like root canal filling material called a guttapercha point. In general, a guttapercha point is comprised of guttapercha as a natural resin and zinc oxide as the major components. A root canal is filled with the material after extirpation of dental pulp.
In order to fill a root canal with a guttapercha point, a method known as the lateral condensation method is usually conducted. This method utilizes two types of guttapercha points of different thickness from each other (a master point and an accessory point). The master point has a thickness which is the same as a reamer or a file which is used for the root canal preparation and is first filled in the root canal. The thin accessory point is then placed in the root canal under pressure in the gap between the root canal wall and the master point. In order to seal the inside of the root canal to a good state by the guttapercha points according to this method, it is necessary to minutely fill the root canal with the guttapercha points. However, since the guttapercha points have extremely low plasticity, it is difficult to completely seal the inside of the root canal. In the event the filling is incomplete, tissue fluid from the root apex is liable to penetrate into the root canal, resulting in inflammation. Also, depending on the case, the guttapercha points protrude out from the root apex, leading to the generation of inflammation. Moreover, in order to achieve lateral condensation, it is necessary to implant a few guttapercha points, so that the operation is very complicated.
In order to overcome the complication of the lateral condensation with guttapercha points, a method has been developed in which a root canal filling material having a relatively low softening temperature is heat softened and then a root canal is filled using a syringe, or the like. However, although the root canal filling material that is presently used for this method has a relatively low softening temperature, when filled in the root canal, it rapidly cools, which decreases its fluidity within an extremely short period of time. For this reason, the root canal filling material hardens before completely filling the root canal, and is thereby likely to result in incomplete filling. Also, drawback occurs which is the inside of the root canal cannot be completely sealed by the root canal filling material because of its low adhesion to the root canal wall and large heat shrinkage.